Rare have been posting developer updates for Sea of Thieves on a regular basis and the latest one mentioned that Xbox One players will get an option to opt out of cross-play with PC, which caused divided reactions from the fan base.
Rare's weekly developer update from 30 January 2019 touched on the subject of cross-play where Joe Neate mentioned that the developers have been listening to the players' feedback regarding this feature. Sea of Thieves is played in first person perspective, so PC players have the obvious advantage of more precise aiming and navigation due to keyboard & mouse input being superior to that of regular controllers.
Therefore, after some Xbox One players asked, Rare decided to give them the option to opt out of cross-play altogether so they can compete on fair terms with other console users. One would think having more options would be a welcome addition, but this is not the case with Sea of Thieves.
Some fans started pondering whether the PC player base would be left to empty servers as they assumed all Xbox One players would opt out, which sparked a controversy between them and the players who like having the option. So far, there is no evidence that PC players would be deserted though, as Rare's studio head, Craig Duncan, stated that player bases are healthy on both Xbox One and PC and the change will not be noticed as the servers will still have the same density.
Furthermore, fans have organised a poll on Reddit, where they can vote on whether they will opt out of cross-play. At the time of writing, less than half of Xbox One players stated they would opt out, meaning there should be enough players for both Xbox One and Xbox One plus PC cross-play servers.
Still, not all players seem to be content, as Sea of Thieves' subreddit is filled with threads regarding the cross-play opt out, with one general thread being pinned to the top of the subreddit.